How to Build Mental Muscle

New research reveals that if you really want that PR, you have to train your brain—hard.

I spring out of bed, pull on my shorts and trainers, slather on sunscreen, and sit down at my computer. It's 7 a.m. on a Sunday morning in mid-May, two weeks before the start of my first marathon, and time for my final big test.

On the screen, an empty road disappears into a blue sky dotted with drifting clouds, rendered in simple '80s-video-game graphics. With a sigh, I empty my mind and click a blue button marked "start," bracing myself for the drudgery ahead. Shapes begin flashing, sometimes to the left of the road and sometimes to the right. When it's a triangle, I hit a button corresponding to its position on the screen, and I do it as quickly as possible, usually within a few hundred milliseconds. When it's a circle, I do nothing. If I fail to respond within two seconds or I respond incorrectly, the screen flashes red and the computer emits an angry buzz.

And that's it. For the next 60 minutes, my sole task is to keep my brain locked on this excruciatingly dull parade of shapes. They flash by rapidly, leaving no time to daydream, check the clock, or even glance out the window. Still, thoughts intrude. I wonder how hot it is outside, whether I should have started earlier...BZZZ. The screen turns red. The longer I continue, the more frequent my mistakes become. When the hour is finally up, I have that cotton-headed feeling of total mental exhaustion that's usually the cue to flop down in front of the TV for a few hours of mindless reruns. Instead, I down a glass of water, step outside, and start running.

I lope through two miles, then gradually squeeze the pace down. I have a 15-mile progression run planned, with the last six at marathon pace. My legs feel fine, but the pace feels tougher than it should, and I have to concentrate hard to sustain it. Once again, I force my brain to zero in on yet another monotonous task: keeping my legs moving and hitting my goal splits. As far as my brain is concerned, the effort feels more like the last 15 miles of a marathon than the first 15.

Which is exactly what I'm aiming for.

There's been a revolution in running science in the last few years. For a century, researchers have focused on the role of the heart, legs, and lungs to explain the limits of human endurance, but they've ignored the brain. Turns out, that was a mistake. It's not lactate levels in your blood or oxygen shortages in your muscles that force you to slow down, it's how your brain interprets those signals. In other words, the effort of running is only as hard as your brain perceives it to be. Scientists have since demonstrated that seemingly absolute physical limits are imposed by the brain—not the body.

But knowing it's your brain that hits the brakes doesn't help if you can't overrule it. So a few researchers scattered around the globe have begun testing methods of harnessing the brain's power: zapping it with electric current, modifying the activity of certain brain regions, or simply training the brain—much like runners train their bodies—to become more fatigue-resistant, so you feel less effort while running at the same pace. This research is still in its infancy, and the outcome is far from clear. But like most runners, I'll try anything for a PR—so I volunteered to be a guinea pig in the brave new era of brain training.

My interest in the role my brain plays in my running goes way back. In 1996, I was a 20-year-old student struggling to break 4:00 for 1500 meters. I'd been running times between 4:00 and 4:02 for three straight years, and seemed to have hit my limit, when I had a breakthrough at an indoor meet in a French-speaking part of Canada. As the timekeeper rushed to translate from French to English, the splits he called out every 200 meters were off by a few seconds. Energized by the notion that I was running faster than ever, I flew to the finish in 3:52, a massive nine-second personal best. What happened next was even stranger: I ran 3:49 and then 3:44 in consecutive races. Whatever had been holding me back had suddenly disappeared—I suspected part of that barrier had been in my head.

That same year, unbeknownst to me, South African physiologist Tim Noakes gave a controversial speech in Cincinnati to members of the American College of Sports Medicine, in which he argued that some of the most cherished pillars of exercise physiology were badly flawed. Noakes himself had introduced thousands of runners—including me—to the concepts behind those pillars, like VO2 max and lactate threshold, with his bestseller The Lore of Running. He'd come to believe that something crucial was missing. The scientific understanding of endurance, as he later put it, was "brainless."

Consider this: If I put a brick on my car's gas pedal and point it down some empty desert highway, the car will keep going until it runs out of gas, blows a tire, or boils its radiator dry. For most of the 20th century, physiologists figured that marathoners operate on similar principles: You go until your muscles run out of glycogen or your legs fail or you get too dehydrated to continue—and then you sputter to a halt. But in the real world, very few marathoners actually reach that breakdown point. Sure, you're tired when you reach the finish line, but you can still hobble to the bagel table. That's because there's a driver in the car, monitoring the warning lights, adjusting pace, and controlling all the components. Noakes's argument was that marathoners have brains, and use them constantly to make sure the body never comes to a dead stop.

It wasn't until I was working as a journalist a decade later that I encountered Noakes's brain-centered view of endurance and the various competing theories it had inspired. I began to notice a series of curious studies pointing to the role of the brain in performance. One showed that cyclists slow down right from the start in hot conditions, long before their bodies have a chance to heat up. Another showed that rigging a thermometer to read falsely low room temperatures allows you to go faster. And others found that given incorrect time or distance feedback, people can go faster.